22 May 1998


Development of teat seals

containing natural bacterial

inhibitors could herald an

end to blanket use of dry

cow therapy.

Emma Penny reports

WITH pressure mounting against blanket use of antibiotics, a new Irish development could help producers prevent mastitis in dry cows without the use of dry cow therapy.

Work at Irelands Moorepark dairy research centre, Fermoy, Co Cork, is investigating the possibility of using teat seals incorporating bacteriocins – which inhibit bac- terial growth – to control mastitis rather than antibiotics.

The project, which also involves Tegascs national dairy products centre at Moorepark and University College, Cork, is led by Moorepark researcher Bill Meaney.

"People have debated the wisdom of prophylactic use of dry cow therapy for several years. In some Nordic countries blanket use has been banned regardless of herd infection status," explains Dr Meaney.

"Where cell counts are reducing, the tendency is to recommend not using dry cow therapy, but thats a dangerous plan as theres a high infection risk during the dry cow period. Also, abrupt drying off can help to reduce cell counts, but doing that without use of antibiotics again increases infection risk."

So despite the pressure to reduce antibiotic use there are risks with ceasing to use dry cow therapy. "Thats why we started looking at non-antibiotic approaches."

Homeopathy was tried, but was found to be rather ineffective.

"Then we started looking at bacteriocins – inhibitory proteins produced by bacteria which kill other organisms."

The processing development centre at Moorepark isolated a bacterium which produced lacticin. This was found to be a natural inhibitor, killing off spoilage bacteria in food, and so Moorepark researchers and UCC began to look at its potential to reduce mastitis concerns.

"We needed to localise the lacticin round the teat orifice, and so started to look at using it with Teatseal," he explains.

Teatseal is usually sold as a two-part treatment – an aqueous antibiotic for use at drying off followed by a seal to prevent entry of new infection. "With the manufacturers of Teatseal we looked at the potential of incorporating the Teatseal plug with lacticin."

In trials, infection-free cows were treated with Teatseal alone and Teatseal plus lacticin at drying off. Bacterial infection – S. dysgalactiae – was then introduced into each quarter to increase the bacterial challenge.

"We were impressed with the results, but really needed to know how it protected against S. aureus, the most likely cause of mastitis."

Trial showed that although lacticin was effective against S. aureus in the lab, it was less effective in cows. "We found that it lost its activity when it became bound up in the seal, but weve now added other agents to the seal which have released it."

Latest trials on cows have shown that lacticin is now effective against S aureus, and researchers are now about to embark on another clinical challenge trial. "We plan to use a big enough bacterial challenge to break down the seal in order to show the value of the lacticin – its difficult to achieve that with a more natural challenge."

Teagasc holds the patent for lacticin, and it will have to go through the medicines board in Ireland before approval for use. However, Dr Meaney hopes that eventually dairy producers will be able to take a more targeted approach towards mastitis control.

"The ultimate aim is for producers to have somatic cell count information for individual cows; those with high cell counts could still be treated with antibiotics, but those at less risk could be treated with the seal plus lacticin." &#42

Mastitis control promises to take a step forward with the development of teat seals containing bacterial inhibitors.


&#8226 Away from prophylactic antibiotics.

&#8226 Lacticin gives control.

&#8226 More targeted approach.

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